U.S. patent application number 10/837177 was filed with the patent office on 2005-03-17 for process for producing (meth)acrylic acid compound.
This patent application is currently assigned to MITSUBISHI CHEMICAL CORPORATION. Invention is credited to Ogawa, Yasushi, Suzuki, Yoshiro, Takasaki, Kenji, Yada, Shuhei.
Application Number | 20050059838 10/837177 |
Document ID | / |
Family ID | 31972986 |
Filed Date | 2005-03-17 |
United States Patent
Application |
20050059838 |
Kind Code |
A1 |
Yada, Shuhei ; et
al. |
March 17, 2005 |
Process for producing (meth)acrylic acid compound
Abstract
A process for producing a (meth)acrylic acid compound, which
comprises distilling acrylic acid, methacrylic acid (these will
hereinafter generally be referred to as "(meth)acrylic acid") or an
ester thereof (these will hereinafter generally be referred to as
"a (meth)acrylic acid compound") in a distillation column to obtain
a purified (meth)acrylic acid compound, characterized in that in
the course of operation of the distillation column including
suspension and resumption of the operation, the distillation column
is washed with water and, thereafter, inside washing with an
organic solvent and/or azeotropic distillation in the presence of
the organic solvent is conducted. In some cases, washing with
alkaline water may be added prior to the washing with water.
Washing of the distillation column for separating and purifying a
crude (meth)acrylic acid compound, can be carried out easily. In
particular, in a process for producing a (meth)acrylic acid
compound, a substance used in a step before or after the
distillation column can be utilized to recover a valuable
substance, and the distillation column can be efficiently
cleaned.
Inventors: |
Yada, Shuhei; (Mie, JP)
; Ogawa, Yasushi; (Mie, JP) ; Takasaki, Kenji;
(Mie, JP) ; Suzuki, Yoshiro; (Mie, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
MITSUBISHI CHEMICAL
CORPORATION
Tokyo
JP
|
Family ID: |
31972986 |
Appl. No.: |
10/837177 |
Filed: |
May 3, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10837177 |
May 3, 2004 |
|
|
|
PCT/JP03/11205 |
Sep 2, 2003 |
|
|
|
Current U.S.
Class: |
560/218 ;
562/600 |
Current CPC
Class: |
B01D 3/143 20130101;
B01D 3/40 20130101; B08B 9/08 20130101; C07C 51/46 20130101; C07C
51/252 20130101; C07C 67/54 20130101; C07C 51/46 20130101; B01J
2219/00006 20130101; C07C 67/54 20130101; C07C 51/44 20130101; B01D
3/14 20130101; C07C 51/252 20130101; C07C 51/215 20130101; C07C
51/44 20130101; B01D 3/36 20130101; C07C 51/215 20130101; C07C
57/04 20130101; C07C 57/04 20130101; C07C 57/04 20130101; C07C
57/04 20130101; C07C 69/54 20130101 |
Class at
Publication: |
560/218 ;
562/600 |
International
Class: |
C07C 069/52; C07C
067/48; C07C 051/42 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 3, 2002 |
JP |
2002-257275 |
Claims
What is claimed is:
1. A process for producing a (meth)acrylic acid compound, which
comprises distilling acrylic acid, methacrylic acid (these will
hereinafter generally be referred to as "(meth)acrylic acid") or an
ester thereof (these will hereinafter generally be referred to as
"a (meth)acrylic acid compound") in a distillation column to obtain
a purified (meth)acrylic acid compound, characterized in that in
the course of operation of the distillation column including
suspension and resumption of the operation, the distillation column
is washed with water and, thereafter, inside washing with an
organic solvent and/or azeotropic distillation in the presence of
the organic solvent is conducted.
2. A process for producing (meth)acrylic acid, which comprises
subjecting propylene, propane or isobutylene to vapor phase
catalytic oxidation to obtain an oxidized reaction mixture,
absorbing the oxidized reaction product in water to obtain an
aqueous solution containing (meth)acrylic acid, concentrating the
aqueous solution in the presence of an azeotropic agent, and
distilling the obtained (meth)acrylic acid in a distillation column
to obtain purified (meth)acrylic acid, characterized in that in the
course of operation of the distillation column including suspension
and resumption of the operation, the distillation column is washed
with water and, thereafter, azeotropic distillation is conducted in
the presence of the azeotropic agent.
3. A process for producing (meth)acrylic acid, which comprises
subjecting propylene, propane or isobutylene to vapor phase
catalytic oxidation to obtain an oxidized reaction mixture,
absorbing the oxidized reaction product in water to obtain an
aqueous solution containing (meth)acrylic acid, concentrating the
aqueous solution in the presence of an azeotropic agent, and
distilling the obtained (meth)acrylic acid in a distillation column
to obtain purified (meth)acrylic acid, characterized in that in the
course of operation of the distillation column including suspension
and resumption of the operation, the distillation column is
preliminarily washed with water, then, with alkaline water and with
water and, thereafter, azeotropic distillation is conducted in the
presence of the azeotropic agent.
4. The process according to claim 1, wherein the organic solvent
has a water content of at most 2 wt %.
5. The process according to claim 1, wherein the organic solvent is
a (meth)acrylic acid compound, methanol, ethanol, butanol, benzene,
toluene, methyl ethyl ketone, methyl isobutyl ketone, methyl
n-butyl ketone, isopropyl acetate, diphenyl ether, biphenyl or a
mixture thereof.
6. The process according to claim 1, wherein the azeotropic
distillation is conducted at a column top temperature of from 20 to
80.degree. C. under a column top pressure of from 0.5 to 120
kPa.
7. The process according to claim 1, wherein the azeotropic
distillation is conducted in the presence of a polymerization
inhibitor.
8. A process for producing a (meth)acrylic acid ester, which
comprises subjecting propylene, propane or isobutylene to vapor
phase catalytic oxidation to obtain an oxidized reaction mixture,
absorbing the oxidized reaction product in water to obtain an
aqueous solution containing (meth)acrylic acid, concentrating the
aqueous solution in the presence of an azeotropic agent, and
purifying the obtained (meth)acrylic acid in a distillation column
and then reacting it with an alcohol to obtain an ester, and
purifying the ester in a distillation column to obtain a purified
(meth)acrylic acid ester, characterized in that in the course of
operation of the distillation column including suspension and
resumption of the operation, the distillation column is washed with
water and, thereafter, inside washing with an organic solvent
and/or azeotropic distillation in the presence of the organic
solvent is conducted.
9. A process for producing a (meth)acrylic acid ester, which
comprises subjecting propylene, propane or isobutylene to vapor
phase catalytic oxidation to obtain an oxidized reaction mixture,
absorbing the oxidized reaction product in water to obtain an
aqueous solution containing (meth)acrylic acid, concentrating the
aqueous solution in the presence of an azeotropic agent, and
purifying the obtained (meth)acrylic acid in a distillation column
and then reacting it with an alcohol to obtain an ester, and
purifying the ester in a distillation column to obtain a purified
(meth)acrylic acid ester, characterized in that in the course of
operation of the distillation column including suspension and
resumption of the operation, the distillation column is
preliminarily washed with water, then, with alkaline water and with
water and, thereafter, azeotropic distillation is conducted in the
presence of an organic solvent.
Description
TECHNICAL FIELD
[0001] The present invention relates to a process for purification
by distillation of acrylic acid, methacrylic acid or their esters.
Particularly, the present invention relates to a washing method at
the time of suspension or resumption of operation of a distillation
column, which is required at the time of separating and purifying
by distillation crude acrylic acid, methacrylic acid or their
esters, obtainable by a vapor phase catalytic oxidation of
propylene, propane or isobutylene. Hereinafter, in the present
invention, acrylic acid and methacrylic acid may generally be
referred to as "(meth)acrylic acid". Further, (meth)acrylic acid
and its ester may generally be referred to as "a (meth)acrylic acid
compound".
BACKGROUND ART
[0002] A distillation method is common as a method for separating
and purifying an acryl monomer such as a (meth)acrylic acid
compound. In recent years, a high performance packing material has
been developed for the purpose of e.g. improving the separation
efficiency by distillation or increasing the amount to be treated
and has been practically employed in distillation columns in
various processes. However, a (meth)acrylic acid compound is
extremely polymerizable, and formation of a polymer in a
distillation column has been a serious problem in a conventional
tray type distillation column, particularly in a high performance
packed column.
[0003] Heretofore, it is known to improve the tray structure (e.g.
JP-A-2000-300903) as a method for preventing formation of a polymer
of a (meth)acrylic acid compound. Further, a method of using a
special polymerization inhibitor (e.g. JP-A-7-53449) has been
proposed. However, it has been difficult to conduct a continuous
operation for a long period of time, and periodical inspection,
washing, repair, etc. have been required, which require suspension
of the operation.
[0004] As a method for such washing or repair, a method has been
proposed which comprises washing with a basic solution of e.g.
sodium hydroxide or potassium hydroxide, followed by washing with a
solvent (particularly preferably water) (e.g. JP-A-2000-319223). In
a case where a (meth)acrylic acid compound is thus treated by a
distillation column, it is common to finally wash the interior with
water for the purpose of safety, in order to inspect the
distillation column during the suspension.
[0005] At the time of resuming the operation after completion of
the inspection, etc. of the distillation column washed with water
as mentioned above, if such water remains in the system, the time
after the resumption of the operation until the distillation column
becomes stabilized in a steady condition, will be prolonged, and a
non-steady operational composition state has to be continued. It
has been found that continuation of this non-steady state brings
about polymerization of the (meth)acrylic acid compound which is a
polymerizable substance.
[0006] Thus, the object of the present invention is to provide a
process for washing a distillation column for separating and
purifying a crude (meth)acrylic acid compound. Particularly, in a
process for producing a (meth)acrylic acid compound, it is to
provide a method for cleaning the distillation column efficiently
in a short time and recovering a valuable substance, by utilizing a
substance used in a process before and after the distillation
column.
DISCLOSURE OF THE INVENTION
[0007] As a result of an extensive study to solve the above
problems, the present inventors have found various facts such as
the following, and have accomplished the present invention;
[0008] (1) The obstruent in the distillation column is composed
mainly of an acidic polymer formed by polymerization of a
(meth)acrylic acid compound, and it will be easily swelled or
dissolved with alkaline water.
[0009] (2) For removal of an alkali component, washing with water
is effective.
[0010] (3) If water is present in a substantial amount in the
distillation column, after resumption of the operation, it takes a
long time until the operation will be in a steady operational
condition.
[0011] (4) In an unstable period after resumption of the operation,
formation of the polymer is substantial.
[0012] (5) Formation of the polymer can remarkably be suppressed by
removing water in the distillation column.
[0013] (6) A substance used in a process before or after the
distillation column, can efficiently be utilized as a dehydrating
agent.
[0014] (7) If an alkali component remains, the (meth)acrylic acid
compound may decomposed.
[0015] Namely, the gist of the present invention resides in a
process for producing a (meth)acrylic acid compound, which
comprises distilling a (meth)acrylic acid compound in a
distillation column to obtain a purified (meth)acrylic acid
compound, characterized in that in the course of operation of the
distillation column including suspension and resumption of the
operation, the distillation column is washed with water and,
thereafter, inside washing with an organic solvent and/or
azeotropic distillation in the presence of the organic solvent is
conducted.
[0016] Further, another gist of the present invention resides in a
process for producing (meth)acrylic acid, which comprises
subjecting propylene, propane or isobutylene to vapor phase
catalytic oxidation to obtain an oxidized reaction mixture,
absorbing the oxidized reaction product in water to obtain an
aqueous solution containing (meth)acrylic acid, concentrating the
aqueous solution in the presence of an azeotropic agent, and
distilling the obtained (meth)acrylic acid in a distillation column
to obtain purified (meth)acrylic acid, characterized in that in the
course of operation of the distillation column including suspension
and resumption of the operation, the distillation column is washed
with water and, thereafter, azeotropic distillation is conducted in
the presence of the azeotropic agent.
[0017] Further, another gist of the present invention resides in a
process for producing (meth)acrylic acid, which comprises
subjecting propylene, propane or isobutylene to vapor phase
catalytic oxidation to obtain an oxidized reaction mixture,
absorbing the oxidized reaction product in water to obtain an
aqueous solution containing (meth)acrylic acid, concentrating the
aqueous solution in the presence of an azeotropic agent, and
distilling the obtained (meth)acrylic acid in a distillation column
to obtain purified (meth)acrylic acid, characterized in that in the
course of operation of the distillation column including suspension
and resumption of the operation, the distillation column is
preliminarily washed with water, then, with alkaline water and with
water and, thereafter, azeotropic distillation is conducted in the
presence of the azeotropic agent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is an example of a process flow chart for producing
acrylic acid by using propylene as the starting material.
[0019] FIG. 2 is another example of a process flow chart for
producing acrylic acid by using propylene as the starting
material.
[0020] FIG. 3 is another example of a process flow chart for
producing acrylic acid by using propylene as the starting
material.
[0021] FIG. 4 is an example of a process flow chart for producing
an acrylic acid ester.
[0022] FIG. 5 is an example of a distillation column for a crude
(meth)acrylic acid compound and its incidental facilities.
DESCRIPTION OF REFERENCE SYMBOLS
[0023] A: Acrylic acid collection column
[0024] B: Dehydration column
[0025] C: Low boiling separation column (acetic acid separation
column)
[0026] D: High boiling separation column (acrylic acid purification
column)
[0027] E: High boiling decomposition reactor
[0028] F: Distillation column having the dehydration column B and
the low boiling separation column (acetic acid separation column) C
joined into one column
[0029] G: Desorption column
[0030] H: High boiling removal column
[0031] K: Solvent recovery column
[0032] L: Esterification reactor
[0033] M: Acrylic acid separation column
[0034] N: High boiling decomposition reactor
[0035] Q: Alcohol extraction column
[0036] P: Alcohol recovery column
[0037] R: Low boiling separation column
[0038] S: Ester purification column
BEST MODE FOR CARRYING OUT THE INVENTION
[0039] The mixture to be treated by distillation in the present
invention is acrylic acid, methacrylic acid or their esters, i.e.
(meth)acrylic acid compounds. For example, acrylic acid may be
mentioned which is obtained by vapor phase catalytic oxidation of
propylene in the presence of a Mo--Bi type composite oxide catalyst
to form acrolein, followed by vapor phase catalytic oxidation in
the presence of a Mo--V type composite oxide catalyst. In such a
case, the process may be a two step reaction wherein a preliminary
reaction of oxidizing propylene to form mainly acrolein and a
subsequent reaction of oxidizing acrolein to form mainly acrylic
acid, are carried out in separate reactors, respectively, or one
step reaction wherein a catalyst for the preliminary reaction and
the catalyst for the subsequent reaction are simultaneously packed
into one reactor to carry out the reactions. Further, the present
invention is also applicable to a process for producing acrylic
acid, which is obtainable by vapor phase oxidation of propane by
means of a Mo--V--Te type composite oxide catalyst or a Mo--V--Sb
type composite oxide catalyst. Further, an acrylic acid ester or a
methacrylic acid ester may be mentioned which is obtainable in a
step of producing such an ester by using (meth)acrylic acid as the
starting material.
[0040] The acrylic acid ester may, for example, be methyl acrylate,
ethyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl
acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate,
2-hydroxypropyl acrylate, or methoxyethyl acrylate. Also with
respect to the methacrylic acid ester, similar compounds may be
mentioned.
[0041] The reaction mixture of the above-mentioned vapor phase
catalytic oxidation is absorbed in water to obtain an aqueous
solution containing (meth)acrylic acid. Such an aqueous solution is
concentrated in the presence of an azeotropic agent such as an
alcohol, a ketone or an aromatic hydrocarbon, whereby crude
(meth)acrylic acid can be obtained. As the azeotropic agent, methyl
ethyl ketone, methyl isobutyl ketone, benzene, toluene or isopropyl
acetate is particularly preferred.
[0042] Such non-purified (meth)acrylic acid compounds include high
boiling point impurities such as a dimer and trimer of
(meth)acrylic acid, their esterified products, maleic anhydride,
benzaldehyde, .beta.-hydroxypropionic acid, .beta.-hydroxypropionic
acid esters, .beta.-alkoxypropionic acid and .beta.-alkoxypropionic
acid esters. The content of the (meth)acrylic acid compound to be
supplied to the distillation column is usually at least 2 wt %,
preferably at least 5 wt %, more preferably at least 10 wt %, in
the present invention. In spite of the low concentration of the
(meth)acrylic acid compound, such impurities and (or) a mixed
composition formed together with water, are often extremely
polymerizable under the temperature and pressure conditions in the
column for the distillation treatment. Yet, such a polymerization
phenomenon is likely to occur at the initial stage of the
distillation operation. Accordingly, the applicable range of the
present invention is wide, and the present invention provides a
substantial effect even in treatment of a process solution
containing a small amount of (meth)acrylic acid compound.
[0043] Namely, distillation of a (meth)acrylic acid compound in the
present invention is usually a step (purification step) of
obtaining a high purity (meth)acrylic acid compound, but is not
limited thereto, and it is applicable also to a step (separation
step) of recovering a component rich in a (meth)acrylic acid
compound from a mixture containing the (meth)acrylic acid
compound.
[0044] Now, the present invention will be described with reference
to the drawings.
[0045] FIG. 1 is an example of a process flow chart for producing
acrylic acid by using propylene as the starting material. The
symbols and numbers in the Fig. are as follows.
[0046] A: Acrylic acid collection column
[0047] B: Dehydration column
[0048] C: Low boiling separation column (acetic acid separation
column)
[0049] D: High boiling separation column (acrylic acid purification
column)
[0050] E: High boiling decomposition reactor
[0051] 1 to 3: Washing solution or polymerization inhibitor-supply
line
[0052] 4: Oxidation reaction gas containing acrylic acid
[0053] 5: Aqueous acrylic acid solution
[0054] 11: Crude acrylic acid
[0055] 15: Acrylic acid discharge line
[0056] 19: High purity acrylic acid discharge line
[0057] An acrylic acid-containing gas obtained by vapor phase
catalytic oxidation of propylene and/or acrolein by using a
molecular oxygen-containing gas, is introduced via a line 4 into an
acrylic acid collection column A and contacted with water to obtain
an aqueous acrylic acid solution.
[0058] Then, the aqueous acrylic acid solution is supplied to a
dehydration column B. In the dehydration column, an azeotropic
agent is supplied, an azeotropic mixture comprising water and the
azeotropic agent is distilled from the column top, and acrylic acid
containing acetic acid, is obtained from the column bottom. The
azeotropic mixture comprising water and the azeotropic agent,
distilled from the top of the dehydration column is introduced into
a storage tank 10, wherein it is separated into an organic phase
composed mainly of the azeotropic agent and an aqueous phase
composed mainly of water. The organic phase is recycled to the
dehydration column B. On the other hand, the aqueous phase is
recycled via a line 7 to the acrylic acid collection column A and
used as collection water to be contacted with the acrylic
acid-containing gas, whereby it can be effectively utilized. Water
is resupplied from a line 8, as the case requires.
[0059] The crude acrylic acid withdrawn from the bottom of the
dehydration column B via a line 11, is introduced into a low
boiling separation column (acetic acid separation column) C in
order to remove the remaining acetic acid. Here, acetic acid is
separated and removed from the column top via lines 12 and 13.
Acetic acid in the line 13 contains acrylic acid, and therefore, a
part or the entire amount may sometimes be returned to the process.
On the other hand, acrylic acid containing substantially no acetic
acid, is obtained from the column bottom via a line 14. This
acrylic acid has a considerably high purity and may be used as it
is, as a material for production of an acrylic acid ester, and in
some cases, will be obtained as a product via a line 15. Acrylic
acid of a still higher purity can be obtained by introducing it via
a line 16 into a high boiling separation column (acrylic acid
purification column) D to separate and remove high boiling point
substances from a line 17 and to obtain highly pure acrylic acid
via lines 18 and 19. The high boiling substances of the line 17 are
led to a high boiling point decomposition reactor E, whereby a part
is recovered as acrylic acid to the process via a line 20. The high
boiling substances will be separated and removed by a line 21.
[0060] FIG. 2 is another example of a process flow chart for
producing acrylic acid.
[0061] This is a process having the dehydration column B and the
low boiling separation column (acetic acid separation column) C in
FIG. 1 joined into one column i.e. a distillation column F, whereby
the flow of the substances is basically the same as in FIG. 1.
[0062] FIG. 3 is another example of a process flow chart for
producing acrylic acid.
[0063] A: Acrylic acid collection column
[0064] G: Desorption column
[0065] D: High boiling separation column (acrylic acid purification
column)
[0066] H: High boiling removal column
[0067] K: Solvent recovery column
[0068] 1 to 3: Washing solution or polymerization inhibitor-supply
line
[0069] 4: Oxidation reaction gas containing acrylic acid
[0070] 5: Acrylic acid-containing solution
[0071] 11: Crude acrylic acid
[0072] 19: High purity acrylic acid-discharge line
[0073] The acrylic acid-containing gas obtained by vapor phase
catalytic oxidation of propylene and/or acrolein by means of a
molecular oxygen-containing gas, is introduced via a line 4 into
the acrylic acid collection column A and contacted with a solvent
to obtain an acrylic acid-containing solution.
[0074] Then, the acrylic acid-containing solution is supplied to
the desorption column G. In the desorption column G, a gas (a gas
of a line 6 discharged from the top of the acrylic acid collection
column A, or a gas after oxidizing and removing organic substances
in the gas in the line 6) is supplied from a line 10, water and
acetic acid are distilled from the column top, and acrylic acid
containing the solvent is obtained from the column bottom. Water
and acetic acid distilled from the top of the desorption column G
are introduced into the acrylic acid collection column A, and water
and acetic acid are finally discharged from the top of the acrylic
acid collection column A. In order to obtain high purity acrylic
acid, acrylic acid from the bottom of the desorption column G is
introduced via a line 11 into a high boiling separation column
(acrylic acid purification column) D, whereby high boiling
substances are separated and removed from a line 14, and high
purity acrylic acid can be obtained via a line 19. The high boiling
substances in the line 14 are specifically maleic anhydride,
benzaldehyde, etc., and they are led to a high boiling removal
column H, whereupon these high boiling point substances are
discharged from a line 21. The solvent from the column bottom is
led via a line 17 to a solvent recovery column K. From the column
top, the recovered solvent is returned via a line 7 to the acrylic
acid collection column A. From the column bottom, via a line 22,
higher boiling substances are separated and removed.
[0075] FIG. 4 is an example of a process flow chart for producing
an acrylic acid ester. The symbols and numbers in the Fig. are as
follows.
[0076] L: Esterification reactor
[0077] M: Acrylic acid separation column
[0078] N: High boiling decomposition reactor
[0079] Q: Alcohol extraction column
[0080] P: Alcohol recovery column
[0081] R: Low boiling separation column
[0082] S: Ester purification column
[0083] 31: Acrylic acid-supply line
[0084] 32: Alcohol-supply line
[0085] 33: Esterification reaction mixture
[0086] 35: Recycled acrylic acid
[0087] 37: High boiling impurity-discharge line
[0088] 39: Crude acrylic acid ester-discharge line
[0089] 41: Water supply line
[0090] 42: Recovered alcohol/water line
[0091] 46: Acrylic acid ester product-discharge line
[0092] Acrylic acid from the line 31, the alcohol from the line 32,
the recycled acrylic acid from the line 35 and the recycled alcohol
from the line 48 are, respectively, supplied to the esterification
reactor L. In the esterification reactor L, a catalyst such as a
strongly acidic ion exchange resin is packed. Via the line 33, the
esterification reaction mixture comprising the formed ester,
unreacted acrylic acid, an unreacted alcohol and formed water, is
withdrawn and supplied to the acrylic acid separation column M.
From the acrylic acid separation column M, the bottom liquid
containing substantially the entire amount of unreacted acrylic
acid, is withdrawn via a line 34 and supplied as a recycled liquid
via the line 35 to the esterification reactor L.
[0093] A part of the bottom liquid is supplied via a line 36 to the
high boiling decomposition reactor N, and a valuable substance
obtained by the decomposition is recycled via a line 40 to the
process. The place within the process where it is recycled, varies
depending upon the process conditions. High boiling impurities such
as oligomers, will be removed out of the system via the line 37.
Further, from the top of the acrylic acid separation column M, the
formed ester, an unreacted alcohol and formed water are distilled
via a line 38. A part of the distillate will be recycled as a
reflux liquid to the acrylic acid separation column M, and the rest
will be supplied via the line 39 to the extraction column Q.
[0094] From the line 41, water for extraction of the alcohol is
supplied, and the water containing the recovered alcohol will be
supplied via the line 42 to the alcohol recovery column P. The
recovered alcohol is recycled via a line 48 to the esterification
reactor.
[0095] From a line 43, the crude acrylic acid ester is supplied to
the low boiling separation column R. Low boiling substances
containing the acrylic acid ester are withdrawn from a line 44 and
will be recycled to the process. The place within the process where
it is recycled, varies depending upon the process conditions. The
crude acrylic acid ester having the low boiling substances removed,
will be supplied via a line 45 to the acrylic acid ester product
purification column S. From the column top, high purity acrylic
acid ester is obtained via the line 46. From the column bottom, a
liquid containing some high boiling substances will be discharged
via a line 47 and recycled to the process. The place within the
process where it is recycled, varies depending upon the process
conditions.
[0096] FIG. 5 is an example of a distillation column for crude
acrylic monomer and its incidental facilities. The numbers in the
Fig. are as follows.
[0097] 51: Distillation column
[0098] 52: Packing material layer or distillation column trays, or
combination of packing material and distillation column trays
[0099] 53: Inhibitor air-supply line
[0100] 54: Heat exchanger for cooling the column top gas
[0101] 55: Heat exchanger for cooling the vent gas
[0102] 56: Reflux drum
[0103] 57: Distributor
[0104] 58: Reboiler (heat exchanger for heating)
[0105] 59: Washing solution or polymerization inhibitor-containing
liquid tank
[0106] 60: Acryl monomer (raw material)-supply line
[0107] 61: Washing solution or polymerization inhibitor-supply
line
[0108] 62: Column top liquid-discharge line
[0109] 63: Column bottom liquid-discharge line
[0110] 64: Vent gas-discharge line
[0111] The line 53 and the lines 61 may be installed at one or more
locations at various portions of distillation depending upon the
conditions of the distillation column.
[0112] The distillation column to which the present invention can
be applied, is all types of distillation apparatus wherein
(meth)acrylic acid compounds are involved in vapor-liquid
equilibrium and is meant for any apparatus to carry out an
operation such as separation, concentration, recovery,
purification, etc. For example, the dehydration column B, the low
boiling separation column (acetic acid separation column) C and the
high boiling separation column (acrylic acid purification column)
D, shown in FIG. 1, correspond thereto. Likewise, the desorption
column G, the high boiling separation column (acrylic acid
purification column) D, the high boiling removal column H and the
solvent recovery column K, shown in FIG. 3, and the acrylic acid
separation column M, the alcohol recovery column P, the low boiling
separation column R and the ester purification column S, shown in
FIG. 4, and the distillation column 51 shown in FIG. 5, correspond
thereto.
[0113] The distillation column may, for example, be a perforated
plate column, a bubble column, a packed column or a combination
thereof (such as a combination of a perforated plate column and a
packed column, see FIG. 5), and any of them may be used in the
present invention irrespective of the presence or absence of an
overflow gate or a downcomer. Specific trays may, for example, be
bubble cap trays, perforated plate trays, bubble trays, super flash
trays, max flux trays, or dual trays.
[0114] As the packing material, in addition to conventional ones of
e.g. columnar, cylindrical, saddle-type, spherical, cubic or
pyramid-shaped, a packing material having a special shape and
having a regular or irregular shape, is commercially available as a
high performance packing material in recent years. Such a material
can preferably be used in the present invention. Such commercial
products may, for example, be, as a regular packing material, a
gauze type regular packing material such as Sulzer Packing
(manufactured by Sulzer Brothers Company), Sumitomo Sulzer Packing
(manufactured by Sumitomo Heavy Industries, Ltd.) or Tecknopack
(manufactured by Mitsui & Co., Ltd.), or MC Pack (manufactured
by Mitsubishi Chemical Engineering Corporation), a sheet type
regular packing material such as Mellapack (manufactured by
Sumitomo Heavy Industries, Ltd.), Tecknopack (manufactured by
Mitsui & Co., Ltd.), or MC Pack (manufactured by Mitsubishi
Chemical Engineering Corporation), or a grid type regular packing
material such as Flexigrid (manufactured by Koch Company). As other
packing materials, GEMPAK (manufactured by Glitsch Company), Montz
Pack (manufactured by Montz Company), Goodroll Packing
(manufactured by Tokyo Tokushu Kanaami K.K.), Honeycomb Pack
(Manufactured by NGK Insulators, Ltd.) or Impulse Packing
(Manufactured by Nagaoka Corporation) may, for example, be
mentioned.
[0115] Further, as an irregular packing material, Raschig ring,
Pall ring (manufactured by BASF), Cascade Miniring (manufactured by
Mass Transfer Company), IMTP (manufactured by Norton Company),
Intalox Saddle (manufactured by Norton Company), Tellerette
(manufactured by Nittetsu Chemical Engineering Ltd.) or Flexiring
(manufactured by JGC Corporation) may, for example, be
mentioned.
[0116] A feature in the present invention resides in that at the
time of washing a polymer deposited and accumulated in the
distillation column after operating the distillation column for a
(meth)acrylic acid compound for a predetermined period of time, (1)
after washing with water, (2) inside flow-down washing with an
organic solvent and/or (3) azeotropic distillation in the presence
of an organic solvent, is carried out. Prior to (2) and/or (3), (4)
washing with alkaline water may be carried out, and such washing
with alkaline water is effective for dissolving the polymer. When
washing with alkaline water is carried out, it is important to
additionally provide (5) a step of washing with water thereafter.
Now, the process will be sequentially described.
[0117] (1) Washing with Water
[0118] It is the main purpose of water to wash out the
(meth)acrylic acid compound remaining in the column. Water is
supplied to the reflux drum of the distillation column and supplied
to the top of the distillation column from the reflux line, or it
may be supplied from the reflux line directly to the distillation
column. The water flows down to the bottom while washing the
interior of the column. In order to let water sufficiently contact
the polymer in the column, the wall of the column, the packing
material in the column, etc. water supplied from the column top and
flows down to the column bottom may be repeatedly supplied from the
column top. In the case of repeated supply, it is preferred to use
the water after separating and removing the solid content in the
flowed down water by e.g. a strainer of a pump. Together with the
supply from the column top, additional supply can be made from the
material supply-stage.
[0119] In a case where a distributor (a liquid distributor or a
liquid distributing nozzle) is installed at an upper portion of the
packed column, it is preferred to adopt a method of supplying water
via such a distributor.
[0120] Washing with water may be carried out usually at a
temperature of from 10 to 100.degree. C. for from 30 to 360
minutes. The amount of water to be supplied may depend also on the
degree of clogging or stain in the column, but is usually from
about 0.5 to 5 m.sup.3/hr per 1 m.sup.2 of the cross-sectional area
of the distillation column (when the water is repeatedly used, the
integrated value thereof).
[0121] In the washing solution thus recovered at the column bottom,
a valuable substance (such as acrylic acid or an acrylic acid
ester) which was remaining in the distillation column immediately
after suspension of the operation, is contained. Accordingly, the
washing solution is once transferred to and stored in a tank, and
after resumption of the operation of the distillation column, it
will be recycled to a proper position within the process (such as
the dehydration column B in FIG. 1) taking into consideration the
composition of the washing solution.
[0122] (2) Inside Flow-Down Washing with Organic Solvent
[0123] The inside washing with an organic solvent is intended for
substitution of water remaining in the column. The organic solvent
to be used for the inside washing, may, for example, be a
(meth)acrylic acid compound, methanol, ethanol, butanol, benzene,
toluene, methyl ethyl ketone, methyl isobutyl ketone, methyl
n-butyl ketone, isopropyl acetate, diphenyl ether, biphenyl, or a
mixture thereof.
[0124] As the organic solvent of the present invention, not only a
high purity solvent as mentioned above, but also an organic solvent
type substance containing various azeotropic agents obtainable from
a process before or after the distillation column, may also be
efficiently used. For example, it is possible to use the azeotropic
agent used for concentration of the aqueous solution containing
(meth)acrylic acid, the crude (meth)acrylic acid obtained by such
concentration, the purified (meth)acrylic acid compound (product)
obtained prior to the suspension of operation of the distillation
column, or an off-specification product recovered at the time of
suspension of the plant.
[0125] The water content in the organic solvent to be used is
preferably at most 2 wt %, more preferably at most 1 wt %. For
example, the product of the (meth)acrylic acid compound usually has
a water content of at most 0.2 wt %, and accordingly, such a
product can be used as it is. Specifically, in the above-mentioned
process charts, it is preferably used for C and D in FIG. 1, D in
FIG. 2 and S in FIG. 3.
[0126] The method for substitution of water by the inside washing
is not particularly limited. For example, it is preferred that the
organic solvent is supplied to a reflux drum of a distillation
column and supplied from a reflux line to the top portion of the
distillation column. The organic solvent which flowed down to the
bottom while contacted with the column wall, the packing material,
the trays, etc. to include water, may be withdrawn to a recovery
system, but in order to carry out sufficient removal of water, it
is preferred to recycle it to the column top or to the
material-supply stage. If the water content in the organic solvent
to be recycled exceeds 2 wt %, the dehydration effect will be
substantially lowered, and such an organic solvent is withdrawn out
of the system. The inside washing with an organic solvent is
usually carried out at a temperature of at most 50.degree. C.,
preferably within a range of from 0 to 40.degree. C.
[0127] The amount of the organic solvent to be used may usually be
from 0.5 to 5 m.sup.3/hr per 1 m.sup.2 of the cross-sectional area
of the distillation column. In a case where removal of the residual
water is difficult from the structure of the interior of the
distillation column, the flow rate may optionally be increased.
[0128] (3) Azeotropic Distillation Cleaning in the Presence of
Organic Solvent
[0129] In the present invention, in order to remove water present
in the column after washing with water, azeotropic distillation
cleaning is carried out in the presence of an organic solvent which
can be azeotropically distilled with water. This step is intended
to remove water, but in a case where a small amount of a polymer is
remaining in the column, its dissolution and removal may be
simultaneously carried out. The water is distilled off from the
top, and the dissolved polymer, etc. will be withdrawn from the
bottom.
[0130] Useful organic solvents include alcohols such as methanol,
ethanol and butyl alcohol, ketones such as methyl ethyl ketone,
methyl-n-butyl ketone and methyl isobutyl ketone, aromatic
hydrocarbons such as benzene, toluene and xylene, and the
above-mentioned (meth)acrylic acid compounds. These organic
solvents may be used in combination as a mixture.
[0131] Such an organic solvent is supplied to the stage for
supplying the distillation stock solution or to the bottom of the
column and will be treated under distillation conditions by a heat
source from a reboiler. As such conditions, the column top
temperature is preferably from 20 to 80.degree. C., and the column
top pressure is preferably from 0.5 to 120 kPa. The water content
of the organic solvent is preferably maintained to be at most 2 wt
%, more preferably at most 1 wt %, whereby the dehydration
efficiency will be excellent.
[0132] (4) Washing with Alkaline Water
[0133] In the present invention, washing with alkaline water is not
an essential step. However, it is thereby possible to dissolve an
acidic polymer and to increase the washing effects. Accordingly, it
may optionally be incorporated as a preliminary step and/or a
subsequent step, of washing with water. In a case where washing
with alkaline water is incorporated, the distillation operation
will be resumed after a step of washing with water and a
dehydration step subsequent thereto.
[0134] As the alkaline water, an aqueous solution of e.g. potassium
hydroxide, sodium hydroxide or sodium carbonate, may be used. With
respect to the concentration, it is used usually within a range of
from 1 to 25 wt %. Further, aqueous ammonia may be used, and with
respect to the concentration, it is used usually within a range of
from 1 to 25 wt %, preferably within a range of from 1 to 10 wt %.
If the concentration is lower than the above range, the washing
efficiency tends to be poor, and if it exceeds the above range, the
heat of reaction with the acid component remaining in the column
tends to increase, whereby formation of a new polymer is likely to
result.
[0135] The alkaline water may be supplied to a reflux drum of a
distillation column and supplied by a reflux line to the top of the
distillation column, or may be supplied directly to the
distillation column from a reflux line. The alkaline water flows
down to the bottom while swelling and dissolving the inside
polymer. In order to let it sufficiently contact with the inside
polymer, the wall of the column, the packing material in the
column, etc., the alkaline water supplied from the top and flows
down to the bottom, may repeatedly be supplied from the column top.
In the case of repeated supply, it is preferred to use it after
separating and removing solid substances contained in the flowed
down alkaline water by e.g. a strainer of a pump. Together with the
supply from the column top, additional supply may be made from the
raw material supply stage.
[0136] In a case where a distributor (a liquid distributor or a
liquid distributing nozzle) is installed at an upper portion of the
packed column, it is preferred to adopt a method of supplying
alkaline water via such a distributor.
[0137] Washing with alkaline water may be carried out usually at a
temperature of from 10 to 100.degree. C. for from 30 to 360
minutes. The amount of alkaline water to be supplied may depend
also on the degree of clogging or stain in the column, but is
usually preferably from about 0.5 to 5 m.sup.3/hr per 1 m.sup.2 of
the cross-sectional area of the distillation column (in the case
where alkaline water is used repeatedly, the integral value
thereof).
[0138] (5) Washing with Water
[0139] In a case where the above-mentioned washing with alkaline
water is carried out, it is important to additionally carry out
washing with water in order to remove the remaining alkali. The
method for washing with water in this case is the same as (1)
washing with water described in the paragraph [0024].
[0140] The water remaining in the column by the inside flow down
washing with an organic solvent or by the azeotropic distillation
cleaning in the presence of an organic solvent, is usually at most
1 wt %, preferably at most 0.5 wt %, more preferably substantially
0. Thus, after resumption of the distillation operation,
on-specification distillation will be quickly possible. If water is
remaining, it will be often a case it takes a long time at a level
of 30 hours until an on-specification state will be reached.
[0141] At the time of the above-mentioned azeotropic distillation
cleaning, a small amount of a polymerization inhibitor may be
supplied. Such a polymerization inhibitor (which may also be called
as a polymerization-suppressing agent, a polymerization-inhibiting
agent, a polymerization-stopping agent or a polymerization
rate-reducing agent) may, for example, be a phenol compound such as
a hydroquinone, methoquinone (methoxyhydroquinone), pyrogallol,
catechol or resorcinol; an N-oxyl compound such as tertiary butyl
nitroxide, 2,2,6,6-tetramethyl-4-hydroxypiperidyl-1-oxyl,
2,2,6,6-tetramethylpiperid- yl-1-oxyl,
2,2,6,6-tetramethylpiperidinooxyl, 4-hydroxy-2,2,6,6-tetramethy-
lpiperidinooxyl, or
4,4',4"-tris-(2,2,6,6-tetramethylpiperidinooxyl)phosph- ite; a
phenothiazine compound such as phenothiazine,
bis-.alpha.-methylbenzyl)phenothiazine, 3,7-dioctylphenothiazine or
bis-(.alpha.,.alpha.'-dimethylbenzyl)phenothiazine; a copper
compound such as cupric chloride, copper acetate, copper carbonate,
copper acrylate, copper dimethyldithiocarbamate, copper
diethyldithiocarbamate, copper dibutyldithiocarbamate or copper
salicylate; a manganese salt compound such as manganese acetate; a
phenylene diamine such as p-phenylene diamine; a nitroso compound
such as N-nitrosodiphenylamine; an urea such as urea; or a thiourea
such as thiourea. These compounds may be used alone or in
combination as a mixture of two or more of them.
[0142] After completion of the washing operation, a prescribed
distillation stock solution containing a crude (meth)acrylic acid
compound is supplied to resume the distillation operation. This
distillation may be carried out by continuous distillation or batch
distillation. The operation conditions for the distillation are
optionally determined taking into consideration the types or
contents of the impurities contained in the crude (meth)acrylic
acid compound, etc., and they are not particularly limited.
Usually, the distillation is carried out at a column top
temperature of from 20 to 80.degree. C., at a column bottom
temperature of from 60 to 120.degree. C. and under a column top
pressure of from about 0.5 to 120 kPa.
[0143] Now, the present invention will be described in further
detail with reference to Examples. However, it should be understood
that the present invention is not limited to such Examples unless
it exceeds beyond its gist.
EXAMPLE 1
[0144] After an inside inspection of a high boiling separation
column (acrylic acid purification column) D in FIG. 1, of which the
operation was suspended for a periodic inspection, an operation for
resumption of the operation was carried out. After the inside
inspection of the high boiling separation column D, the inside was
washed with water to remove the stain formed during the
operation.
[0145] The high boiling separation column was a distillation column
made of stainless steel (SUS316) having an internal diameter of
1100 mm and a height of 20000 mm and having 21 perforated plates,
and using such a column, distillation of crude acrylic acid was
carried out. Prior to the distillation, 1000 kg of an acrylic acid
product containing 0.03 wt % of water, supplied to a reflux drum
56, was supplied to the high boiling separation column from the
top. The supplied liquid flowed down to the bottom, and the liquid
collected at the bottom was discharged from the bottom portion of
the column. The water content of the discharged acrylic acid was 3
wt %.
[0146] Therefore, 1000 kg of the same acrylic acid product was
again supplied to the reflux drum 56, and a similar washing and
substitution operation was carried out. The water content in the
acrylic acid discharged from the bottom was 0.2 wt %. From the
starting material supply line 60, a mixture comprising 98.5 wt % of
acrylic acid as a crude acryl monomer, 0.3 wt % of maleic acid, 0.2
wt % of an acrylic acid dimer, 0.0.02 wt % of water and other high
boiling substances, was supplied at a rate of 1300 kg/hr. Further,
from the tank 59 for a polymerization inhibitor-containing liquid,
liquids having 8 wt % of methoquinone and 1 wt % of phenothiazine
dissolved in acrylic acid, were supplied at rates of 34 kg/hr and
31 kg/hr, respectively. The heat source was supplied, and the
inside pressure, etc. were adjusted, and after about 5 hours, the
operation became stable at a column top pressure of 2.8 kPa at a
bottom pressure of 8.4 kPa at a column top temperature of
53.degree. C. and a bottom temperature of 78.degree. C. from the
column top, high purity acrylic acid having a water content of 0.02
wt % and a purity of at least 99.8 wt %, was obtained. With respect
to the operation, a continuous operation for 1 year was
possible.
COMPARATIVE EXAMPLE 1
[0147] Distillation was resumed in the same manner as in Example 1
except that in Example 1, inside substitution with acrylic acid was
omitted. In the acrylic acid obtained from the top of the column by
the resumption of the operation, 0.7 wt % of water was contained.
The water content gradually decreased, and about 36 hours were
required until the water content became 0.02 wt %. As the
distillation was continued under the water excessive state, the
bottom pressure of the distillation column gradually increased, and
after one month, the bottom pressure became 18 kPa, whereby the
operation was terminated. As a result of the internal inspection, a
large amount of a polymer was detected.
EXAMPLE 2
[0148] After an inside inspection of a low boiling separation
column R in FIG. 4, of which the operation was suspended for a
periodic inspection, an operation for resumption of the operation
was carried out. After the inside inspection of the low boiling
separation column R, the inside was washed with water to remove the
stain during the operation.
[0149] The low boiling separation column R was a distillation
column as shown in FIG. 5, made of stainless steel (SUS304) and
having an internal diameter of 1100 mm and a height of 26000 mm and
having 36 perforated plates (dual trays) installed inside, and
using such a column, a distillation of crude ethyl acrylate was
carried out.
[0150] Prior to the distillation, 800 kg of an ethyl acrylate
product having a water content of 0.002 wt %, supplied to a reflux
drum 56, was supplied to the low boiling separation column from the
top. The supplied liquid flowed down to the bottom, and the liquid
collected at the bottom portion was discharged therefrom. The water
content of the discharged ethyl acrylate was 3.6 wt %.
[0151] Therefore, 1000 kg of the same ethyl acrylate product was
supplied again to the reflux drum 56, and a similar washing and
substitution operation was carried out. The water content in the
ethyl acrylate discharged from the bottom was 0.11 wt %. A similar
operation was conducted again, and as a result, the water content
in the ethyl acrylate discharged from the bottom was 0.004 wt %. A
mixture comprising 97.4 wt % of ethyl acrylate as the crude acryl
monomer, 1.8 wt % of water, 0.4 wt % of acrylic acid, 0.4 wt % of
ethanol and 0.1 wt % of ethyl acetate, was supplied at a rate of
6000 kg/hr. Further, from a tank 59 for a polymerization
inhibitor-containing liquid, a liquid having 5 wt % of hydroquinone
dissolved in ethanol, was supplied at a rate of 60 kg/hr. A heat
source was supplied, and the inside pressure, etc. were adjusted,
and after about 7 hours, the operation became stable at a column
top pressure of 62.7 kPa at a bottom pressure of 72.7 kPa at a
column temperature of 76.degree. C. and a bottom temperature of
89.degree. C. Ethyl acrylate having a water content of 0.001 wt %
and a purity of at least 99.1 wt %, was obtained from the bottom.
During the operation, the difference in pressure between the column
top and the column bottom (hereinafter referred to as the pressure
difference) was stable during the operation, and a continuous
operation for one year was possible.
COMPARATIVE EXAMPLE 2
[0152] The distillation was resumed in the same manner as in
Example 2 except that in Example 2, the inside substitution with
ethyl acrylate was omitted. Initially, ethyl acrylate obtained from
the bottom contained 3.1 wt % of water. The water content gradually
decreased, and about 53 hours were required until the water content
became 0.001 wt %. The distillation was continued under a water
excessive state, whereby from the resumption of the operation, the
bottom pressure of the distillation column gradually increased, and
after one month, the bottom pressure became 82 kPa, whereby the
operation was terminated. As a result of the inside inspection, a
large amount of a polymer was detected.
EXAMPLE 3
[0153] After an inside inspection of a dehydration column B in FIG.
1, of which the operation was suspended for a periodic inspection,
an operation for resumption of the operation was carried out. After
the inside inspection of the dehydration column B, the inside was
washed with water in order to remove the stain during the
operation.
[0154] The dehydration column B was a distillation column made of
stainless steel (SUS316L), having an internal diameter of 4000 mm
and a height of 25000 mm and having 30 perforated plates, and using
such a column, distillation of crude acrylic acid was carried
out.
[0155] Prior to the distillation, toluene was supplied to the
reflux drum at a rate of 5000 kg/hr and supplied to the high
boiling separation column from the top. The supplied liquid flowed
down to the column bottom, and after confirming the liquid surface
at the bottom, a heat source was supplied. From the column top,
distilled toluene and water were discharged. After about 5 hours,
there was no more distillation of water. During this period, there
was no discharge from the bottom.
[0156] From the starting material supply line, a mixture comprising
60 wt % of acrylic acid as a crude acryl monomer, 0.4 wt % of
maleic acid, 4 wt % of acetic acid, 35 wt % of water and other high
boiling substances, was supplied at a rate of 7500 kg/hr. Further,
from the drum for a polymerization inhibitor-containing liquid, a
liquid having 0.6 wt % of copper acetate and 4 wt % of hydroquinone
dissolved in acrylic acid was supplied at a rate of 6 kg/hr, and a
liquid having 2 wt % of phenothiazine dissolved in toluene, was
supplied at a rate of 500 kg/hr. At the same time, supply of
toluene from the reflux drum was stopped, and toluene distilled
from the column top was refluxed and balanced to maintain the
liquid level of the reflux drum, while a part was withdrawn out of
the system.
[0157] A heat source was supplied, and the inside pressure, etc.
were adjusted, and after about 6 hours, the operation became stable
at a column top pressure of 15.9 kPa at a bottom pressure of 22.7
kPa at a column top temperature of 46.degree. C. and a bottom
temperature of 82.degree. C. From the bottom, acrylic acid having a
water content of 0.01 wt % and a purity of at least 74 wt %, was
obtained. With respect to the operation, a continuous operation for
one year was possible.
COMPARATIVE EXAMPLE 3
[0158] The distillation was resumed in the same manner as in
Example 3 except that in Example 3, the initial distillation by
toluene was omitted. At the resumption of the operation, acrylic
acid obtained from the bottom contained 2 wt % of water. The water
content gradually decreased, and about 62 hours were required until
the water content became 0.01 wt %.
INDUSTRIAL APPLICABILITY
[0159] By employing the process of the present invention, washing
of a distillation column for separating or purifying a
(meth)acrylic acid compound can be carried out easily.
Particularly, in a process for producing a (meth)acrylic acid
compound, it is possible to recover a valuable substance and to
effectively wash the distillation column by utilizing a substance
used in a process before or after the distillation column. Further,
at the resumption of the distillation operation after the washing,
on-specification stabilized operation will quickly become
possible.
[0160] The entire disclosure in the specification of Japanese
Patent Application No. 2002-257275 from which the priority is
claimed in this application, is incorporated herein by reference in
its entirety.
* * * * *